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Skilled baristas know that achieving the perfect complex flavor profile for a delectable shot of espresso is as much art as science. Get it wrong, and the resulting espresso can taste too bitter or sourly acidic rather than being a perfect mix of each. Now, as outlined in a new paper in the journal Matter, an international team of scientists has devised a mathematical model for brewing the perfect cup, over and over, while minimizing waste.

"A good espresso beverage can be made in a multitude of ways," said co-author Christopher Hendon, a computational chemist at the University of Oregon. "The point of this paper was to give people a map for making an espresso beverage that they like and then be able to make it 100 times in a row."

There's actually an official industry standard for brewing espresso, courtesy of the Specialty Coffee Association, which sets out strict guidelines for its final volume (25-35mL, or roughly one ounce) and preparation. The water must be heated to 92° to 95°C (197° to 203°F) and forced (at a specific pressure) through a bed of 7 to 9 grams (about a quarter of an ounce) of finely ground coffee over the course of 20 to 30 seconds. But most coffee shops don't follow this closely, typically using more coffee, while the brewing machines allow baristas to configure water pressure, temperature, and other key variables to their liking. The result of all those variations in technique is a great deal of variability in quality and taste.

"Most people in the coffee industry are using fine-grind settings and lots of coffee beans to get a mix of bitterness and sour acidity that is unpredictable and irreproducible," said Hendon. "It sounds counterintuitive, but experiments and modeling suggest that efficient, reproducible shots can be accessed by simply using less coffee and grinding it more coarsely."

The flavors in espresso derive from roughly 2,000 different compounds that are extracted from the coffee grounds during brewing. So Hendon and his colleagues focused on building a mathematical model for a more easily measurable property known as the extraction yield (EY): the fraction of coffee that dissolves into the final beverage. That, in turn, depends on controlling water flow and pressure as the liquid percolates through the coffee grounds. Modeling the actual grounds—a form of granular media—proved much too daunting. "You would need more computing power than Google has to accurately solve the physics and transport equations of brewing on a geometry as intricate as a coffee bed," said co-author Jamie M. Foster, a mathematician at the University of Portsmouth in the UK.

Instead, Hendon, Foster, and their colleagues based their model on how lithium ions propagate through a battery's electrodes, which they liken to how caffeine molecules dissolve from coffee grounds. A bunch of simulations and several thousand experimental shots of espresso later (courtesy of Frisky Goat Espresso in Brisbane, Australia), the authors arrived at some surprising findings.

For instance, conventional wisdom holds that a fine grind is best, since more surface area of the resulting tamped-down coffee bed is exposed to the hot water, thus boosting the extraction yield. But this new model, and the group's experiments, revealed that if coffee is ground too finely, it can clog the coffee bed, thereby reducing extraction yield. It's also a big factor in the variability in taste. The researchers concluded that there are better methods for maximizing extraction yield, such as using fewer beans and coarser grinds with a bit less water. And the Specialty Coffee Association might be interested to hear that brew time is largely irrelevant.

"Though there are clear strategies, there is no obvious optimal espresso point."

Coffee is a multi-billion dollar global industry. In 2015 alone, according to the authors, just the US market accounted for some 1.5 million jobs and generated $225.2 billion in revenue. But climate change (along with changing customer tastes) is threatening coffee producers, sparking interest in finding ways to maintain quality while cutting costs and reducing waste. This new model should lend insight into precisely how one might accomplish that, although there is still some wiggle room to account for subjective personal preferences in the flavor profile.

"Though there are clear strategies to reduce waste and improve reproducibility, there is no obvious optimal espresso point," said Hendon. "There is a tremendous dependency on the preferences of the person producing the coffee; we are elucidating the variables that they need to consider if they want to better navigate the parameter space of brewing espresso."

Based on a year-long trial waste reduction protocol set up at a local specialty coffee shop in Eugene, Oregon, the authors estimate that a small cafe could save several thousand dollars per year by reducing the mass of coffee used, while the industry as a whole could conceivably save as much as $1 billion per year.

"The real impact of this paper is that the most reproducible thing you can do is use less coffee," said Hendon. "If you use 15 grams instead of 20 grams of coffee and grind your beans coarser, you end up with a shot that runs really fast but tastes great. Instead of taking 25 seconds, it could run in 7 to 14 seconds. But you end up extracting more positive flavors from the beans, so the strength of the cup is not dramatically reduced. Bitter, off-tasting flavors never have a chance to make their way into the cup."

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Modeling the actual grounds—a form of granular media—proved much too daunting. "You would need more computing power than Google has to accurately solve the physics and transport equations of brewing on a geometry as intricate as a coffee bed," said co-author Jamie M. Foster, a mathematician at the University of Portsmouth in the UK.

Isn't this close to what was occupying the 'Heart of Gold' shipboard computer in Douglas Adams' Hitchhiker's Guide to the Galaxy? Odd, how parallel prior fiction and resulting reality can be..

I don't have the book handy but I believe the shipboard drink synthesizer was stumped on how to make tea for Arthur, and it enlisted the help of the shipboard computer (don't remember if that was Eddie) who was also having difficulty as well, and it almost got them killed, I think from Magrathean warheads that eventually got turned into a bowl of petunias and a sperm whale (one of which ended up being agrajag)..

But this is from memory so the exact near death event might be a little off..

Oh I thought you were referencing the part about computational physics and particles.

I don't drink espresso, not enough time to enjoy is for the expenses involved. SCA guidelines are that, guidelines, a great starting point. there's room for fine adjustments

I use a Orphan Espresso Lido E manual grinder, brew in a chemex, and use a scale accurate to 1/10th a gram.

that's an important part for a consistent cup, measure your ingredients in weight. recommended ration 16:1 water:coffee grounds. temp 195-205. watch your brew time to make sure your grind is right. let your taste buds guide you on fine tuning the variables for what coffee you use.

I prefer some coffees a touch stronger usually no more than 15.8:1 though. may make tiny adjustments to the grind.

The aeropress community, which is far more open to experimentation than the espresso scene, has also been following a trend toward coarser grind and shorter infusion times, but along with this has come a trend toward higher brew ratios (more coffee to water), which is not what this researcher is pursuing.

But the taste objective is essentially the same: to get more of the fruity acidity that extracts quickly and less of the bitter astringent flavors that take longer to extract. In an aeropress, infusion time can be controlled independently of grind size (especially with inverted method), whereas with espresso, those two variables are tightly related to each other. My favorite aeropress recipe has a total time of 90 seconds (20 bloom, 40 infuse, 30 press), and I use a medium-coarse grind size about halfway between drip and french press.

There are some nifty tricks going on in the espresso community, too. Scott Rao discovered that by sandwiching the coffee puck between two aeropress paper filters (one in the bottom of the portafilter and one on top of the puck), he could grind extra-fine (almost Turkish grind) without clogging the machine and running a really slow shot. The filters distribute the water evenly and efficiently through the coffee, resulting in a higher extraction ratio.

This is more in line with what this researcher is pursuing. It seems fairly obviously that the hypothetical brewing method that uses coffee most efficiently will use a fine grind to maximize surface-to-area ratio -- but not if the grind is so fine that the brewing apparatus isn't extracting evenly and filtering cleanly. Because the performance of an espresso machine (in its typical configuration) is so sensitive to grind size, it's difficult to evaluate the impact of different grind sizes independently of the knock-on effects.

I don't drink espresso, not enough time to enjoy is for the expenses involved. SCA guidelines are that, guidelines, a great starting point. there's room for fine adjustments

I use a Orphan Espresso Lido E manual grinder, brew in a chemex, and use a scale accurate to 1/10th a gram.

that's an important part for a consistent cup, measure your ingredients in weight. recommended ration 16:1 water:coffee grounds. temp 195-205. watch your brew time to make sure your grind is right. let your taste buds guide you on fine tuning the variables for what coffee you use.

I prefer some coffees a touch stronger usually no more than 15.8:1 though. may make tiny adjustments to the grind.

Would love to get into turkish coffee more

Turkish coffee is great and wonderfully cheap and easy to prepare – especially if you have a gas stove. Only downside is that it takes a bit longer than machine-made espresso – because the taste is nicest when you bring it to a slow boil.

I don't drink espresso, not enough time to enjoy is for the expenses involved. SCA guidelines are that, guidelines, a great starting point. there's room for fine adjustments

I use a Orphan Espresso Lido E manual grinder, brew in a chemex, and use a scale accurate to 1/10th a gram.

that's an important part for a consistent cup, measure your ingredients in weight. recommended ration 16:1 water:coffee grounds. temp 195-205. watch your brew time to make sure your grind is right. let your taste buds guide you on fine tuning the variables for what coffee you use.

I prefer some coffees a touch stronger usually no more than 15.8:1 though. may make tiny adjustments to the grind.

Would love to get into turkish coffee more

Turkish coffee is great and wonderfully cheap and easy to prepare – especially if you have a gas stove. Only downside is that it takes a bit longer than machine-made espresso – because the taste is nicest when you bring it to a slow boil.

I've made it before, although without the the proper pot. was great still. would get a dedication grinder too, mine still struggles with that fine-ness

I quickly realized that most store brands were terrible and go stale almost immediately unless you move them promptly to a vacuum sealed coffee tin. I found that the grinder needs to be adjusted for each bean\brand and that letting the water sit in the grinds for any more than 3-4 minutes hurts more than helps. I'm currently trying to work out if a different coarseness works better for lighter vs darker roasts. I have to say, I've made some really atrocious cups of joe in the past months, but when I nail it, it's almost transcendental...

Welcome to one of the most delightful, pedantic and maddening pastimes humanity has come up with.

Indeed. I'm just amazed that I've been a dedicated coffee drinker for 25 years and yet I'm just now really beginning to appreciate it properly.

I quickly realized that most store brands were terrible and go stale almost immediately unless you move them promptly to a vacuum sealed coffee tin. I found that the grinder needs to be adjusted for each bean\brand and that letting the water sit in the grinds for any more than 3-4 minutes hurts more than helps. I'm currently trying to work out if a different coarseness works better for lighter vs darker roasts. I have to say, I've made some really atrocious cups of joe in the past months, but when I nail it, it's almost transcendental...

Welcome to one of the most delightful, pedantic and maddening pastimes humanity has come up with.

Indeed. I'm just amazed that I've been a dedicated coffee drinker for 25 years and yet I'm just now really beginning to appreciate it properly.

Handy shortcut: go to a local coffee roaster and ask the people there to grind you the coffee you're buying, then match yours to that at home. One thing that surprised me when I started buying the Serious Gourmet Shit, as Jules Wynfield would say, is that it really isn't much if any difference in price between Big Box brands' best stuff (still crap) and a local roaster that makes substantially better coffee.

Personally, I was surprised by how fine the "coarse" grind from my local roaster's shop was compared to "coarse" as defined by the clapped-out grocery store burr grinder.

I once was looking up papers on a certain type of optical spectroscopy and came across one entry which described using this method to fingerprint different vintages of wine. That must have been a ...fascinating grant proposal to write.

Don't be so quick to dismiss. If that worked, it is/would be a great tool to find counterfeit wine.

I once was looking up papers on a certain type of optical spectroscopy and came across one entry which described using this method to fingerprint different vintages of wine. That must have been a ...fascinating grant proposal to write.

Don't be so quick to dismiss. If that worked, it is/would be a great tool to find counterfeit wine.

It has so many more uses than that. Colorimetry is an important part of an enologist's analytical toolkit. Lots of important factors about the product can be inferred from even slight alterations to, say, near-IR absorption. This stuff doesn't seem important until you're trying to QC hundreds or thousands of hectoliters of wine for mass production.

Apparently my Italian grandmother, RIP, you were a wonderful woman, was a covert scientist. She made the most incredible espresso and cappuccinos. And the espresso was a main ingredient in her tiramisu. How I miss it.

I quickly realized that most store brands were terrible and go stale almost immediately unless you move them promptly to a vacuum sealed coffee tin. I found that the grinder needs to be adjusted for each bean\brand and that letting the water sit in the grinds for any more than 3-4 minutes hurts more than helps. I'm currently trying to work out if a different coarseness works better for lighter vs darker roasts. I have to say, I've made some really atrocious cups of joe in the past months, but when I nail it, it's almost transcendental...

Welcome to one of the most delightful, pedantic and maddening pastimes humanity has come up with.

Indeed. I'm just amazed that I've been a dedicated coffee drinker for 25 years and yet I'm just now really beginning to appreciate it properly.

Handy shortcut: go to a local coffee roaster and ask the people there to grind you the coffee you're buying, then match yours to that at home. One thing that surprised me when I started buying the Serious Gourmet Shit, as Jules Wynfield would say, is that it really isn't much if any difference in price between Big Box brands' best stuff (still crap) and a local roaster that makes substantially better coffee.

Personally, I was surprised by how fine the "coarse" grind from my local roaster's shop was compared to "coarse" as defined by the clapped-out grocery store burr grinder.

That's a good idea. My current grinder is handheld hand-cranked though so while it can get very fine, the finer I set it the harder it is to grind and longer it takes. It came as a package with what I guess would be considered a travel-French-press-mug. Great for camping and it's started me on this path but I sense that I'm going to have to upgrade soon. I still have my decades old plugin grinder that works more like a mini food processor, but I'm pretty sure it's been thoroughly ruined by grinding spices for cooking.

I quickly realized that most store brands were terrible and go stale almost immediately unless you move them promptly to a vacuum sealed coffee tin. I found that the grinder needs to be adjusted for each bean\brand and that letting the water sit in the grinds for any more than 3-4 minutes hurts more than helps. I'm currently trying to work out if a different coarseness works better for lighter vs darker roasts. I have to say, I've made some really atrocious cups of joe in the past months, but when I nail it, it's almost transcendental...

Welcome to one of the most delightful, pedantic and maddening pastimes humanity has come up with.

Indeed. I'm just amazed that I've been a dedicated coffee drinker for 25 years and yet I'm just now really beginning to appreciate it properly.

Handy shortcut: go to a local coffee roaster and ask the people there to grind you the coffee you're buying, then match yours to that at home. One thing that surprised me when I started buying the Serious Gourmet Shit, as Jules Wynfield would say, is that it really isn't much if any difference in price between Big Box brands' best stuff (still crap) and a local roaster that makes substantially better coffee.

Personally, I was surprised by how fine the "coarse" grind from my local roaster's shop was compared to "coarse" as defined by the clapped-out grocery store burr grinder.

That's a good idea. My current grinder is handheld hand-cranked though so while it can get very fine, the finer I set it the harder it is to grind and longer it takes. It came as a package with what I guess would be considered a travel-French-press-mug. Great for camping and it's started me on this path but I sense that I'm going to have to upgrade soon. I still have my decades old plugin grinder that works more like a mini food processor, but I'm pretty sure it's been thoroughly ruined by grinding spices for cooking.

I quickly realized that most store brands were terrible and go stale almost immediately unless you move them promptly to a vacuum sealed coffee tin. I found that the grinder needs to be adjusted for each bean\brand and that letting the water sit in the grinds for any more than 3-4 minutes hurts more than helps. I'm currently trying to work out if a different coarseness works better for lighter vs darker roasts. I have to say, I've made some really atrocious cups of joe in the past months, but when I nail it, it's almost transcendental...

Welcome to one of the most delightful, pedantic and maddening pastimes humanity has come up with.

Indeed. I'm just amazed that I've been a dedicated coffee drinker for 25 years and yet I'm just now really beginning to appreciate it properly.

Handy shortcut: go to a local coffee roaster and ask the people there to grind you the coffee you're buying, then match yours to that at home. One thing that surprised me when I started buying the Serious Gourmet Shit, as Jules Wynfield would say, is that it really isn't much if any difference in price between Big Box brands' best stuff (still crap) and a local roaster that makes substantially better coffee.

Personally, I was surprised by how fine the "coarse" grind from my local roaster's shop was compared to "coarse" as defined by the clapped-out grocery store burr grinder.

Store grinders are a crap shoot at the best of times. aside from being contaminated by flavored beans, the grind issues are due to the fact that most of the time those machines aren't calibrated after factory. and few people in the store know how to run one, let alone calibrate it. That besides, the fact that most grindmasters (what most stores use) have poorly designed burr configurations, with one burr spring loaded allowing for higher variability on grind size. Dittings may be build well, but they trade some consistency for speed.

Get grinder for home, a good one (like a baratza encore), will do wonders for the quality of your cup of liquid gold

I quickly realized that most store brands were terrible and go stale almost immediately unless you move them promptly to a vacuum sealed coffee tin. I found that the grinder needs to be adjusted for each bean\brand and that letting the water sit in the grinds for any more than 3-4 minutes hurts more than helps. I'm currently trying to work out if a different coarseness works better for lighter vs darker roasts. I have to say, I've made some really atrocious cups of joe in the past months, but when I nail it, it's almost transcendental...

Welcome to one of the most delightful, pedantic and maddening pastimes humanity has come up with.

Indeed. I'm just amazed that I've been a dedicated coffee drinker for 25 years and yet I'm just now really beginning to appreciate it properly.

Handy shortcut: go to a local coffee roaster and ask the people there to grind you the coffee you're buying, then match yours to that at home. One thing that surprised me when I started buying the Serious Gourmet Shit, as Jules Wynfield would say, is that it really isn't much if any difference in price between Big Box brands' best stuff (still crap) and a local roaster that makes substantially better coffee.

Personally, I was surprised by how fine the "coarse" grind from my local roaster's shop was compared to "coarse" as defined by the clapped-out grocery store burr grinder.

That's a good idea. My current grinder is handheld hand-cranked though so while it can get very fine, the finer I set it the harder it is to grind and longer it takes. It came as a package with what I guess would be considered a travel-French-press-mug. Great for camping and it's started me on this path but I sense that I'm going to have to upgrade soon. I still have my decades old plugin grinder that works more like a mini food processor, but I'm pretty sure it's been thoroughly ruined by grinding spices for cooking.

The manual grinder scene is stronger than ever, and the quality is better than ever. although the higher end ones will be pricier than powered ones. Orphan Espresso are still great, they've improved the design since I got mine, fixing a big issue on mine. Kinu appears to be making some waves, but they're even more expensive. nicer manual grinder are fast enough that you can easily grind it in the time it takes to boil your water. otherwise, go for a baratza, lots of people swear by them

I do think some of the comments on this thread are hilarious in terms of how persnickety people are about preparing their espresso shots. I'm expecting "and then I whisper tender nothings to the grounds so they are ultimately relaxed for the extraction" or "I only get my beans ground under the light of a full moon touched only by the hands of a virgin" shortly. I'm sure it does change the taste of the resultant brew, but good lord it reads like OCD.

Eh, we tea snobs aren't any better. "I use free trade Kenyan first-flush leaf with fresh ginger grown only by local small farm leprechauns, water flown in from Antarctic glaciers boiled and let cool for exactly 2.36 minutes, and strain with a solid gold mesh obtained from the blood of free-range dragons."

Modeling the actual grounds—a form of granular media—proved much too daunting. "You would need more computing power than Google has to accurately solve the physics and transport equations of brewing on a geometry as intricate as a coffee bed," said co-author Jamie M. Foster, a mathematician at the University of Portsmouth in the UK.Instead, Hendon, Foster, and their colleagues based their model on how lithium ions propagate through a battery's electrodes, which they liken to how caffeine molecules dissolve from coffee grounds. A bunch of simulations and several thousand experimental shots of espresso later (courtesy of Frisky Goat Espresso in Brisbane, Australia), the authors arrived at some surprising findings.

Extraction from a packed bed has been addressed in many, many ways in literature (and textbooks - this topic is very old science) with various simplification approaches applied to avoid need for universe-sized computer. I expect the team could of reached the same conclusions by just using Perry's Chemical Engineers' Handbook for sourcing appropriate design equations rather than developing yet another model, but that's the difference between mathematicians and engineers, isn't it?

I have a quite expensive set up at my house after years of being disappointed by espresso from my local shops. I don't experiment with brew ratios as much as I'd like just because I'm averse to wasting pricey coffee (I generally use ratios provided by the roaster). I'm going to have to buy some average coffee and play around using what I learned in this article.

My local coffee shop doesn't use an espresso roast. They roast their own coffee and use a lighter roast for their espresso. I have found it's more in the ramp down then anything else. If the barista doesn't tamp it down right it will taste bad. Most barely do it at all.

I just wasted a quarter pound of coffee trying this shit. I feel like the authors of the study owe me $4.

Switched my Rancilio grinder from its tried and true setting of 4 to 15. Carefully measured out 18 grams of coffee and tamped hard. The shot came out in about 12 seconds, but it produced no crema at all. Moreover, my espresso machine never reached the 7-9 bars I normally see for good extraction. Tried again with an even harder tamp. No joy. Switched my grinder to an 8. Same thing.

The lure of using less coffee and shaving off 10 seconds of shot time was strong. Now I'm back to my regular settings: lots of coffee (25 grams?), super fine grind, 25 seconds shots = lotsa of crema and good flavor.

I just wasted a quarter pound of coffee trying this shit. I feel like the authors of the study owe me $4.

Switched my Rancilio grinder from its tried and true setting of 4 to 15. Carefully measured out 18 grams of coffee and tamped hard. The shot came out in about 12 seconds, but it produced no crema at all. Moreover, my espresso machine never reached the 7-9 bars I normally see for good extraction. Tried again with an even harder tamp. No joy. Switched my grinder to an 8. Same thing.

The lure of using less coffee and shaving off 10 seconds of shot time was strong. Now I'm back to my regular settings: lots of coffee (25 grams?), super fine grind, 25 seconds shots = lotsa of crema and good flavor.

Scientific studies suck.

Dude, they said coarser not your grinder's coarsest setting! For all you know your original coarseness setting already matched their final iteration's.

"a barista is able to achieve highly reproducible espresso with the same EY as the 20 g espresso by reducing the coffee mass to 15 g and counter-intuitively grinding much coarser (as shown in red, Figure 6B). This modification may result in very fast shots (<15 s), a reduction in espresso concentration, and a different flavor profile."

And

"It is clear that espresso made at 22% EY in the partially clogged regime tastes more “complex” than a fast 22% EY obtained using the optimization routine presented in Figure 6."

Emphasis mine. This study isn't about finding a better method; it is about reducing waste. The article overblows the findings a bit. The study only claims a 25% reduction in coffee usage. With a typical shot being 15g of espresso that means 12.5g. That may be because they mention mixing the low dose shot with a regular one to improve the flavor profile. So, I'm not even going to try this one out.

I've tried lots of different beans in my beloved Gaggia espresso machine, and found that the ground that works for one bean, doesn't for the next. YMMV, basically.

I don't like the Robusta blends that are used in most fancy office machine - they are usually bitter (bitter does NOT equal taste) and contain twice the caffeíne of Arabica. The difference between the two was apparantly not part of the study, which makes me doubt the general validity of the outcome.

Interesting study, I have found that grinding up beans too fine makes the coffee a bit too bitter. Coffee grind consistency works even for espresso.My twice daily drink is Seattle's Best Blend #4 made with an Aeropress. Those two together is likely better than any other coffee or espresso youve ever had.

My sister bought me an Aeropress a while back and I don't think I've ever managed to get a decent cup of coffee out of it. Considering how much I've heard people have about it, I must be doing something wrong.

These days I go with the mocha pot, but the consistency isn't quite there, regardless of how much I fiddle with my burr grinder, temperatures and filling. It's usually pretty good, sometimes amazing and sometimes not so good.

My preferred method is actually a simple, fairly manual, DeLonghi espresso machine. We're in the (long) process of moving, though, and it's been boxed up. Consistency is very solid, grinding halfway between finest and medium on my grinder. Lightly tamped using just the weight of the solid iron tamper. Preferred bean is a Lavazza - either gold or espresso roast. We've tried a ridiculous number of different beans, from all the big brands to specialty roasts in the shops and freshly roasted local blends. We always come back to to the Lavazza. Maybe we're just boring.

I've tried lots of different beans in my beloved Gaggia espresso machine, and found that the ground that works for one bean, doesn't for the next. YMMV, basically.

It can even vary for the same beans, depending on age. Back when I still made espresso at home, and bought good beans within a couple of days of roasting, I tended to find I had to adjust the grind as the beans aged.

A bunch of simulations and several thousand experimental shots of espresso later (courtesy of Frisky Goat Espresso in Brisbane, Australia), the authors arrived at some surprising findings.

"The findings were reported in one extremely long sentence. written in 30 seconds without punctuation or spaces, and witnesses reported the authors were vibrating strongly enough to register on nearby seismographs."

Heh, I fake judged some baristas as training before a competition. 13 espressos later, with no spitting out anything, and I did register on a seismograph. Caffeine is a drug. Confirmed!

- Grind enough coffee to fill my portafilter. My grinder is weight-based, so I dial that in and generally only change the weight when I change beans. Currently it's set to 16g.- Try to tamp 30lbs the first time, turning the tamper clockwise. Then rotate the portafilter ~90 degrees and tamp 15lbs the second time, turning counter clockwise. I am sure my weights are off as I haven't practised on a scale in probably 5+ years.- A double shot should come out at 8-9 bars of pressure and take about 25 seconds. If it's coming out too fast, I adjust to a finer grind. Too slow and I make the grind coarser. I adjust the grind every couple days as the coffee needs different grind settings as the beans age. Plus of course there's the variability in my tamping.

Doing things in this manner more or less follows the general standard espresso guidelines above and yields fairly reproducible coffee, notwithstanding the occasional dud due to bad tamping, new coffee, etc.

What you mention I believe applies more to a reproducible way than what is discussed in the article. Consistency in the way you make it is key, especially tamping, which requires practice, not science. I often think an engineers mind is better at making coffee as a scientist would take all day to make one cup.

You're certainly right, but the other side of the argument is that people have been tasting and dialing in espresso preferences for ~100 years now. The "official industry standard" referred to in the article is mostly the result of this century or so of experience with what generally makes a good espresso.

Based on my own experience of trying to make good espresso, trying more or less coffee, different grind settings, longer or shorter shots, plus the coffee I buy and the equipment I have, and my own personal taste preferences, I think in the end most of us who are spending way too much time trying to make good espresso and being scientific in our endeavours end up doing much of what this article suggests.

Our goal was exact 18 - 22 second shots that fill both shot glasses to the fill lines. With the machine at identical pressure settings. You could certainly taste the difference: too packed and it takes way too long and you get burned bitter product. Leave it in too long and it gets sour and undrinkable at 30 seconds. Too little packing and it is too fast and you get weak product. Unmatched shot glasses and you are tamping poorly. (Top of the line La Marzocco, I forget the grinder brand)

Not rocket science, but man that was good coffee. The whole pacific northwest coffee scene remains superior imo. Still, you can now do better than the burnt diarrhea they serve at Starbucks pretty much anywhere else as well.

That's a good idea. My current grinder is handheld hand-cranked though so while it can get very fine, the finer I set it the harder it is to grind and longer it takes. It came as a package with what I guess would be considered a travel-French-press-mug. Great for camping and it's started me on this path but I sense that I'm going to have to upgrade soon. I still have my decades old plugin grinder that works more like a mini food processor, but I'm pretty sure it's been thoroughly ruined by grinding spices for cooking.

I use a manual Hario Skerton* to grind my beans, and I find that it's easier to do a fine grind for the drip coffeemaker than it is a coarse grind for cold brew. Fine grinds don't have little "boulders" that need a little extra effort to crush.

1.5 rotations from cinched down for drip and 3 rotations for cold brew.

* modified with a bracket to reduce wiggling and have a more consistent coarse grind.